Millimeter-wave technology is a wireless technology that can provide up to multi-Gigabits per second (Gbps) wireless connectivity between electronic devices. The frequency range of millimeter-wave application is significantly higher than those used for FM radio. Millimeter-wave technology can exploit unregulated bandwidth that is available world-wide and with better efficiency and security than traditional wireless LAN frequencies. In addition, higher frequencies mean shorter wavelengths. As a result, the antenna systems can be millimeter size. However, the electrical distribution of such millimeter-wave-band radio frequency signals over air is limited due to the high transmission loss.
Millimeter-wave radio-over-fiber (RoF) techniques and systems are drawing more and more research and commercial interest in part due to the seamless integration of huge transmission bandwidth with optical fiber communication and flexible wireless access provided by optical fiber and high-frequency RF carriers: (W. Jian et al., “Energy-Efficient Multi-Access Technologies for Very-High-Throughput Avionic Millimeter Wave, Wireless Sensor Communication Networks,” IEEE J. of Lightw. Technol., Vol. 28, No. 16, pp. 2398-2405, Aug. 15, 2010); (G. Chang et al., “Broadband Access Technologies for Very High Throughput Wireless Sensor Communication Networks,” IEEE Radio and Wireless Symposium'09, January 2009).
Photonic generation and up-conversion of millimeter-wave signals play important roles in millimeter-wave system design: (A. Wiberg et al., “Fiber-optic 40 GHz Millimeter-wave link with 2.5 Gb/s data transmission,” IEEE Photon. Technol. Lett., vol. 17, no. 9, pp. 1938-1940, September 2005); (H. Song et al., “Error-free simultaneous all-optical upconversion if WDM radio-over-fiber signals,” IEEE Photon. Technol. Lett., vol. 17, no. 8, pp. 1731-1733, August 2005).
The traditional schemes of millimeter-wave signal generation, such as double-sideband (DSB) and optical carrier suppression (OCS), experience a performance-fading problem and a limitation of transmission distance. As a result, the typical DSB millimeter-wave signal suffers severe deterioration after 40-km single-mode-fiber (SMF) transmission.
In (J. Yu et al., “Optical Millimeter-Wave Generation or Up-Conversion Using External Modulators,” IEEE Photon. Technol. Lett., vol. 18, no. 1, pp. 265-267, January 2006), the generated or up-converted optical millimeter wave using OCS modulation scheme shows high receiving sensitivity, high spectra efficiency, and small power penalty. However, uneven amplitudes of optical carrier at 40 GHz after 40-km SMF transmission caused by fiber dispersion are also experienced. After 60-km SMF transmission, due to fiber dispersion and large carrier-to-sideband ratio (CSR), the eye diagram is almost closed. Furthermore, more components are adopted for millimeter-wave generation by using DSB or OCS. For example, an extra local oscillator is required for up-conversion.
Millimeter-wave signals are generally generated with a single-sideband (SSB) scheme. However, the typical millimeter-wave generation with SSB is complex. For example, an extra optical modulator or interleaver is employed in a SSB scheme. In (J. Yu et al., “A Novel Scheme to Generate Single-Sideband Millimeter-Wave Signals by Using Low-Frequency Local Oscillator Signal,” IEEE Photonics Technology Letters, vol. 20, no. 7, pp. 478-480, Apr. 1, 2008), for example, millimeter-wave is generated by using SSB modulation with a low-frequency local oscillator. Moreover, an additional external optical filter or interleaver is deployed to filter out the first-order modes, which makes the generation scheme more costly.